(1) Field of the Invention
The present invention relates to a process for optically joining an optical fiber array to an opponent member.
(2) Related Art Statement
In order to optically join an optical fiber to an opponent member such as an optical waveguide, it is necessary to coincide a center of a core of the optical fiber with an optical center of the opponent member. For this purpose, an optical fiber array is first prepared by fixing the optical fiber betweena a V-grooved base plate and a fixing base plate, and this optical fiber array is aligned with the opponent member. In order to accurately effect this alignment, the following processes have been heretofore developed and investigated.
According to a first process, an optical fiber array and an opponent member are placed on respectively separate stages, a light beam is projected into the optical fiber array as an input terminal, and the optical fiber array is joined to the opponent member after alignment through which one or two stages are finely moved to maximize a power of the light beam emitted from the opponent member maximum. This process is the most general and practical process currently performed. However, the process requires a complicated system, and complexity and cost required for the completion of the joining pose great problems.
According to a second process, a guide groove is formed in an optical fiber array and a corresponding guide groove is formed in an opponent member. Then, alignment is effected between them by inserting a guide pin into both the guide grooves. However, this process has the problem in that it takes time to form the guide grooves. In particular, since the guide groove must be formed on the opponent member without grinding the upper surface thereof when the opponent member is an optical waveguide substrate, it is very difficult to attain given accuracy.
According to a third process, an optical fiber array is aligned with an opponent member by using given outer surfaces of the optical fiber array and the opponent member as reference surfaces. This process is very attractive in that the alignment is automatically effected only by inserting both the array and the opponent member into a given package. However, there has been no manufacturer who has succeeded in the actual industrial development of this third process, which is now under development.
When the optical fiber is to be optically connected to the opponent member according to the third process, it is considered to be a common practice that an optical fiber array is formed by accurately locating optical fibers by using a V-grooved base plate 1 and a fixing base plate 2 as shown in FIG. 1, and the optical fiber array is joined to the opponent member by using a bottom surface of the V-grooved base plate as a reference surface, while an optical center of the opponent member 50 is coincided with centers of cores of the optical fibers. A plurality of V-grooves 3 for fixing bared optical fibers and a recess 4 for receiving a tape-shaped covering of the optical fibers are formed in the V-grooved base plate 1. In the fixing base plate 2 are formed a flat surface portion for fixing the bared portions of the optical fibers in the respective V-grooves 3 and a recess 5 for receiving the covering. The V-grooves are formed in such a dimension that when the optical fibers are fitted to the respective V-grooves and the fixing base plate is placed on the optical fibers, each of the optical fibers is brought into close contact with opposite inclined surfaces of the V-groove and the flat surface of the fixing base plate, so that the optical fibers are accurately located and the fixing base plate is accordingly accurately held on the optical fibers.
However, since the V-grooved base plate 1 needs to be bonded to a surface of a glass plate or the like with an adhesive in order to work the V-grooves 3 for fixing the optical fibers in the base plate 1, occurrence of a dimensional error of around .+-.30 .mu.m resulting from the adhesive layer cannot be avoided. Therefore, the distance A from a reference bottom face of the glass plate bonded to the base plate 1 to the opposite surface thereof, that is, to the vertical position of the V-groove, has a variation in a range of about .+-.30 .mu.m. As a result, it is necessary to effect fine adjustment in alignment between the optical fiber array and the opponent member 50 not only in a horizontal direction but also in a vertical direction, so that much time is required to effect the aligning and joining works.